Testing of solutions



F. J. CAHN 2,471,861

- TESTING SOLUTIONS May 31, 1949.

Filed May 14,- 1945 INVENTOR, wJa /W Q 'BZQL .fi-

Patented May 31, 1949 2,471,861 resume or soLU'rrons Frank 3. .Cahn, Chicago, Ill., assior to rat Emulsol Corporation, ilhieago, Illaa corporation of Illinois Application May n, was, semi No. scams (or. cs-ccoi 7 illaims. t My invention relates to the testing of aqueous solutions of either anionic compounds or cationic quaternary ammonium compounds to determine the concentration thereof, the invention having particular utility in connection with the testing of dilute solutions of certain types of cationic quaternary ammonium compounds as hereinafter described in detail. I

Quaternary ammonium compounds containing a lipophile group, such as an aliphatic hydrocarbon chain of about 12 carbon atoms or more, are used in industry for a variety of purposes as, for example, germicides, bactericides, antiseptics, preservatives, detergents, ore flotation agents;

emulsifying agents, textile treating agents, and

the like. Such compounds are, in general, of high potency and it is common practice, therefore, to utilize them in dilutions of the order of l part to 1000 parts of Water or in even materially greater dilutions. These low concentrations render it important, particularly for field testing and control work, to have available a test method which is accurate and rapid and which may be carried out with simple equipment.

It has heretofore been suggested to test or determine the concentration of quaternary ammonium compounds by a method which comprises forming a salt of the quaternary ammonium compound contained in the solution thereof to be tested with bromothymol or bromophenol blue in aqueous sodium carbonate solution, extracting.

the colored salt which is formed with ethylene dichloride, drying the non-aqueous layer with sodium sulfate, filtering, and measuring the intensity of color so extracted by means of a photoas the cost and availability of the particular equipment required.

In accordance with my present invention, the determination of the concentration of a cationic quaternary ammonium compound in the form of a dilute aqueous solution thereof is measured by virtue of certain changes which take place by th addition thereto of an equivalent amount of an anionic compound. More specifically, I have found that, when a few drops of dichlorofluorescein indicator solution are added to a dilute colorless or substantially colorless solution of particular cationic quaternary ammonlmn compound employed. When this solution is titrated with a dilute solution of an anionic compound,

the pink or reddish color appears at or near th equivalence point. I have also found that this color change can be more easily observed and the equivalence point more sharply perceived by in troducing a waterdmmisollole organic solvent into the system, particularly suitable solvents being chlorinated compounds illustrative examples or which are ethylene dichloride and chloroform. The organic solvents become colored when in equilibrium with the aqueous phase containing the free cationic quaternary ammonium compound and lose the color whcnthe system becomes void of the tree cationic quaternary ammonium compound after the addition oi the equivalent amount of anionic compound to the system. The color changes are reversible, making back titration readily feasible.

In an illustrative example of the practice of the method of my present invention, 25 cc. of the solution of the cationic quaternary ammonium compound to be tested, the concentration or which solution is of the order of 0.001 M or less, are placed in a cc. stoppered tube or cylinder, 5 cc. of chloroform and 3 drops of a 0.1% dichlorofluorescein alcohol solution are then added, and the mixture is shaken. The resulting chloroform-in-water emulsion becomes colored pink and, if the emulsion is allowed to separate, the upper aqueous layer and the lower chloroform layer appear pink in transmitted light. A standardized dilute aqueous solution of an anionic compound is then added gradually, in portions, with shaking after each addition, until the emulsion is only faintly colored. At this step, the chloroform layer settles out rapidly. Finally, the anionic solution is added in an amount completely to discharge the pink color from the chloroform layer. This is the end point of the titration.

In the table below, there is a summary of the results obtained by the use of the method of the present invention in connection with illustrative cationic quaternary ammonium compounds, using certain illustrative anionic compounds for the titration. The values obtained were calculated by reference to compound No. 4

involved, 1 it being understood that commercial 1 mixtures of the appropriate long-chain alcohols or fatty acids, rather than a single alcohol or a q single fatty acid, were employed in the preparation of the cationic quaternary ammonium. com-- pounds and anionic compounds. In, all cases,

also, the cationic quaternary ammonium-compounds and the anionic. compounds utilized were purified samples of commercially available materials. That is, the inorganic salts present in the commercially available materials were extracted by boiling with 90% aqueous isopropanol followed by recrystallization froma suitable-solvent.

, 4 1 In the accompanying drawings, I show a testing kit which is particularly satisfactory for use in the field in accordance with my present invention and wherein Figure 1 represents a perspective view of a carrying case and reagent bottles and testing tube or cylinder disposed therein, and

Figure 2 shows the remainder of the reagent botties and testing tube or cylinder comprising the kit removed from the carrying case.

The carrying case [0 comprises front and rear walls H and II, respectively; side wallsll3. and i4, bottom it and a cover H which is adapted to be closed in anysuitable manner as,- for ex ample, by means of snaps. The case is partitioned so as to provide a'seriesof pockets or compartments, preferably six in number.- As shown in Figure 1, a stoppered bottle l8, a dropper bottle I! and a graduated testing tube 'TabZe Conven- Value by tlonal Value Anioniomated Conventional Against No. Com mind- (Mean Catlomc p Analysis Molecular Titrafiy Weight) tion 7 1 ouna-mcnmpni- Volhard ass ass 1. 2 v

'Cetyl trimethyl ammonium bromide I 2 cam -mod-cm-so -Ho-mm-Nfle 4 Monoe'thanolamine salt oilaurylsulioacetatc I a V Y C ,H; OSO Na Suliated AshL--- 304 307 4 I Sodium lauryl sulfate 4 t 4 [C H; C0+O CgH4NHC0- CHg-N C l- Volhard 470.5 5, 2, 3

N (palmitic acid ester of colamino iormylmethyl) pyridinium chloride 5 CnHrh-CO O-C HA -NHCO- CHr-SO K Suliated Ash.--. 405 391 4 Laurie acid ester of monoethanolamlne sulfoaeetomide, potassium salt 6 [OnHn N 1 1- Voihard 380.2 338 2 Lauryl pyridinium iodide t 7 [CnHz1 CO-O-C;H4-NH CO-Cfi:N(C;H5)s]+Cl- ..--.d0 440 462.5 I 2 N (myristic acid ester of colamino formylmethyl) triethylamnionium chloride 1 Commercial long chain alkyl materials were employed in the preparation of the compounds listed above. 2 Compound No. 4 (molecular weight 470.5 as indicated by Volhard chlorine titration) was used as a primary standard.

aEach of the Compo A sample calculation for compound No. 5 is as follows, using. as stated above, compound No. 4

as the standard. A solution was prepared by dissolving 0.4036 gramof compound No. 4 (mean which equals 0.000359 N. lit requiredf21.30 cc.

of a. solution of compound No. 5 (containing 0.400 gram per liter of water) to titrate cc. of the aforementioned solution Hence,

be noted, :compares very favorably with the value "of 405 which was obtained by a sulfated ash deof compound No. 4.

' unds" comprises a mixture ofhomoloaues. the formula of the listed homologue being that which most closely approaches the mean molecular weight as determined by Conventional Analysis."

or cylinder 2i are disposed, each in one pocket, of the case I. A stoppered bottle 22, dropper bottle '23'and graduated testing tube 24, shown in Figure 2, are adapted to fit into the remaining pockets of the case and comprise the balance of to time, may be replenished from the bottle l8 which, it will be noted, hasa substantially larger capacity than does the dropper bottle IS. The

, in which case M, the equivalent weight oflcom-" pound No. 5, equals 397. value for M, itwill graduated testing tube 2| is provided with lines or markings and identifying indicia.

The bottle 22 serves to hold a supply of the I fluorescein dissolved, preferably, in ethylene dichloride or carbon tetrachloride or other similar water-immiscible organicsolvent. The dropper bottle 23 servesfalso to hold a solution of the fluorescein which, from time to time, may be retermination (a sample of 0.3197 gram-of com I poundNo. 5, when ashed in the presence-of sul- I fuirlc; acid, gave 0.0688 gram of potassium sulfa e ' bottle 23'.

plenished from the bottle 22, the latter having a substantially larger capacity than dropper The graduated testing tube 24 is identical with the tube 2|,

compounds may vary.

In the use or the kit, the tube 1| (or ll) is first rinsed and well drained and there is then added thereto, up to the line marked "Test Sample," the aqueous solution of thecationic quaternary ammonium compound to be tmted. The indicator solution is then added from dropper bottle 23 by means oithe dropper to the line marked Indicator Solution A, whereupon the tube 2i is stoppered and well shaken. The color of the solution will be pink unless there is no cationic quaternary ammonium compound present or unless the concentration thereof is substantially negligible in the solution being tested. The standard anionic compound solution is then added from dropper bottle it up to the line marked 1:12500, the tube It is stoppered and shaken about ten times and then allowed to settle. I! the lower layer is colorless, the test is complete, showing that the concentration or strength or the cationic quaternary ammonium compound is 1212500 or less. If, however, the lower layer is still pink, additional anionic compound solution is added up to the line marked 1:6500, the solution shaken and allowed to settle as before. These operations oi shaking and allowing to settle are repeated, in each case the solution of the anionic compound being added to the next succeeding line, until the lower layer is substantially colorless. At this stage, the concentration of the cationic quaternary ammoni compound is read directly on the tube ii, at the highest liquid level therein. The concentration of cationic quaternary ammonium compound read on the tube 2i may be translated readily into terms oi ounces per gallon or the like and a suitable table may be provided to facilitate this conversion. Thus, for example, a reading ct 1:12500 on the tube M is equivalent to approximately 1 ounce of cationic quaternary ammonium compound per 100 gallons (U. S.) or water and a reading of 1:2500 on the tube 2!] is equivalent to about 1 ounce of the cationic quaternary ammonium compound per 20 gallons (U. S.) of water.

Since the cationic quaternary ammonium compounds are incompatible with soaps and alkaline washing compounds, the tubes II and 24, after each test, should be rinsed with plain tap water only, that is, without the addition thereto of soaps or alkaline washing compounds.

In general, the dilute solutions of the anionic compounds or cationic quaternary. ammonium compounds which are used as standards should be freshly prepared until their. stability has been adequately investigated. In this connection, it

, will be appreciated that the stabllitm under ordinary storage conditions, of the various anionic compounds and cationic quaternary ammonium The ethanolamine salt of lauryl sulioacetate, in the form of a 0.001 M solution at a pH of 5.65, for example, remains constant titrimetrically for at least three months when stored under usual conditions in an or-.

dinary glass bottle. As a general rule, it is convenient to make up the standard solutions of anionic compounds or cationic quaternary ammonium compounds to a concentration of 0.4 gram per liter, which corresponds to a molarity of 0.001. Other concentrations may, of course, be employed.

I have found that the method of my present invention is well adapted to the determination. in dilute aqueous solutions, of such cationic quaternary ammonium compounds as have an effective lipophile group, particularly an uninterrupted aliphatic carbn chain of not less than about 12 carbon atoms. The quaternary nitrogen may be part of a heterocyclic ring, such as a pyridine ring, or it may comprise alkyl, aryl,

till

aralkyl or alkylol substituted ammonia. These criteria must apparently be satisfied, coupled with those set out below in relation to the anionic compounds, in order to obtain accurate or reasonably accurate quantitative determinations. The anionic compounds should also contain a iipophile group having not less than about 12 carbon atoms, particularly, in an uninterrupted carbon chain, and a hydrophile group. in the form of an oxygenated sulphur or phosphorus radical such as a sulfate, suifonate, orthophosphate, pyrophosphate, tetrophosphate or metaphosphate radical in the form of a salt thereof such as a sodium, potassium, ammonium, ethanolamine or other salt. in general, the optimum pH range for the titration medium is approximately 5.5 to i.

As I have indicated above,.the method oi my present invention may be used for the determine. tion of the concentration, in dilute aqueous solu tions, of various anionic compounds. in this case, the cationic quaternary ammonium compound is made up in the form of a standard dilute aqueous solution of known concentration and is used to titrate the solution of the anionic com pound of unknown concentration. The testinti kit, in this case, would be modified only by substituting, in the bottles it and it, a dilute stand ardiecd solution of a cationic quaternary am monium compound for the standardized anionic compound solution. In the titration proper, the end pointoccurs when the color of the chloro form layers turns from colorless to pink.

What I claim as new and desire to protect by Letters Patent of the United States is:

1. In a method of determining the concentration, in dilute aqueous solutions, of .a member se-' lected from the groups consisting of (i) cationic quaternary ammonium compounds containing a chain of not less than about 12 carbon atoms, and (2) anionic compounds of the type which contain an uninterrupted carbon chain of not less than about 12 carbon atoms and a radical selected from the group consisting of salts of sulfonates and sulfates, the steps which comprise providing a measured volume of a dilute aqueous solution of a compound falling into one of said groups of compounds, admixing therewith a small proportion of dichlorofluorescein; and then titrating with a dilute aqueous solution of known concentration of a compound falling into the other of said groups of compounds. i

2. In a method of determining the concentration,.in dilute aqueous solutions, of a cationic quaternary ammonium compound containing a chain of not less than about 12 carbon atoms, the steps which comprise providing a measured volume of .the dilute aqueous solution of said cationic. quaternary ammonium compound, admixing therewith a substantially lesser amount of a water-immiscible organic solvent and a fraction of a percent of dichlorofluorescein, and then titrating with a dilute aqueous solution of known concentration of an anionic compound of the type which contains an uninterrupted carbon chain of not less than about 12 carbon atoms and a radical selected from the group consisting of salts of sulfonates and sulfates.

chain oi not less than about 1 2 carbon'atoms and wherein the quaternary nitrogenis part 01. a pyridine ring, the steps which comprise providing a measured volume 01 the dilute aqueous solution of said cationic quaternary, ammonium compound,

admixing therewith a substantially lesser amount taming from 12 to 18 carbon atoms and where the three valence bonds connected to N are directlyv attached to carbon, and said anionic compound comprising an oxygenated sulfur derivative containing an uninterrupted carbon chain of from 12x0 18 carbon atoms.

of a water-immiscible organic solvent, in the form" of a chlorinated compoimd, and a'fraction ota percent of dichlorofiuorescein', and then titrating,

with 'ajdilute aqueous solution or knownconcentration of an anionic compound of the type which contains an uninterrupted oarbon ch'ain of not less than about 12 carbon atoms anda-radical selected from the group consistingflof'salts of an]: j

fonates and sulfates.

quaternary ammonium compound containing a chain of not less than about 12 carbon'atomsj'the steps which-comprise providing a measured volume of the dilute aqueous solution'of said'ca'tionic quaternary ammonium compound, admixing therewith a small amount of dichlorofluorescein,

and then titrating with a dlluteaqueous solutionor known concentration-of an anionic compound of the type which contains an'uninterrupted carhon-chain of not less thanabout 12 carbon atoms and a radical selected from the group consistingof salts of sulfonates and sulfates 5. In a method of determining the concehtramm, in dilute aqueous'solutions, of a cationic uaternary ammonium compound, the steps which comprise providing a measured volume of the dilute aqueous solution of said'cationiczquaternary ammonium compound,-admixing therewith a substantially lesser amount ofta watereimmiscible 1 organic solvent and a fraction of a percent of dic'hlorofluore'scein,,and then titratingwith a dilute aqueous solution of known concentration of an anionic compound, said cationic quaternary.

l5 4; In a method-of determining thefconbeatra- 7 'tion, in dilute aqueous solutions, ota cationic 6. In-a method ordetermining the concentration,'in dilute aqueous solutions, of an anionic. compound of the type'which foontainslhn uninl0 terrupted'carbon chain of' notJless than about12' group consisting of salts of sultonates and sulrates, the steps which comprise providing a measured volume of the dilute aqueous solution of said anionic compound, admixing therewith, a small proportion of dichlorofluoresceimand then titrating with a'dilute'aqueoussolution'pf known concentration or a cationic quaternary ammonium compound containing comm of notless than 12 v carbon atoms. v

7. In a method of determining the concentration, in 'dilute'aqujeous solutions, of an anionic compound of the type which contains an uninterrupted'carbpn chainot not less than about 12 carbon atoms and a radical selected from the group cohsisting'of'salts of sulfonates and sulfates, the steps ;which'comprise providing a measured volf ume of the dilute aqueous solution 01' said anionic 1 compound, admixing therewith a substantially lesser amountofa water-immiscibleuorganic solventjand a fraction of a percent of dichloro- 1 fluores'cei'n, andithen titrating with'a dilute aqueammonium compound-corresponding to the for is an aliphatic carboxylic acid acvlradieal conous, solution of known concentration of a cationic quaternary ammonium compound containing a j chain of not less than about 12-carbon atoms.

1 t F 1 mm; J. CAI-IN. REFERENCES crrnn.

The ;'following tile. or. this patent UNITED s'ra'ras ra'rnn'rs Name l Date 1,674,416 .Taylor .-June 19, 1928 1,986,403 Lehmkuhl Jan. 1, 1935' 2,370,683 'Palma Mar. 6, 1945 OTHER- REFERENCES,

Auerback. ,-Industrial*& Engineering Chem.

, Anal. Ed., 15 (1943),:pp. 492 and 49?.

carbon atoms and a f i ical-selected-irom thereferences are of record in the 

